Ventilation Perfusion relationships Flashcards
Distribution of ventilation (awake, upright, spont):
during END-expiration. what area of the lung is more subatmospheric and what area is less subatmospheric
Non-dependent (apex) more subatmospheric
Dependent (base) less Subatmospheric
Distribution of ventilation (awake, upright, spont):
with END-Inspiration what are in more and less subatmspheric
non-dependent more subatmospheric
Dependent less subatmospheric
Distribution of ventilation (awake, upright, spont):
ventilation = what?
change in volume
Distribution of ventilation (awake, upright, spont):
since ventilation is a change in volume… where is ventilation the best in this patient???? and why?
the dependent lung
b/c there is teh biggest change in volume done there. the alveoli went from empty to full. and the non-dependent alveoli went from 1/2 full to full. see picture on next slide
Distribution of ventilation (awake, upright, spont):
picture of why ventilation is best in the dependent lung of this pt
what is normal V/Q mismatch and why?
0.8
Normal MV is 4L/min
Normal CO is 5L/min
4 / 5 = 0.8
Distribution of ventilation (awake, upright, spont):
so where is ventilation the best in this pt
dependent lung
Distribution of Perfusion (awake, upright, spont):
where is perfusion the best during end -expiration at and why?
the dependent lung
b/c the alveoi are smaller and gets best blood flow
in the non-dependent lung the alveoli are large and compress the vasculature.
ex nondependent has a V/Q of 3.5
where dependent has V/Q of 0.6
(see picture on next slide)
Distribution of Perfusion (awake, upright, spont):
picture to explain why perfusion is best in bases
Distribution of Perfusion (awake, upright, spont):
so where is perfusion best in this pt?
dependent bases
in the diagram show how Intrapleural pressure, Ventilation, perfusion, V/Q mismatch, PaO2 and PaCO2 differ in the dependent and non-dependent lung.
pt is upright and spont breathing
Distribution of V/Q: Lateral Decubitus UNanesthetized:
in the spont breathing pt in lateral decubitus, what happens to the V and Q in the lungs to the dependent and non-dependent lungs
Same is in the upright pt.
dependent lung always the down lung
Distribution of V/Q: Lateral anesthetized & paralyzed:
what happens to V and Q and V/Q mismatch here? and why?
Ventilation best to NON-dependent (up) lung
Perfusion best to Dependent lung (down)
Increased V/Q mismatching
the dependent lung becomes compressed by the abd contents. with positive pressure ventilatin, inspiratory gases are preferentaly distributed to the NON-dependent lung. A clinically significant mismatch in V/Q develops. The NON-dependent lung is well ventilated but poorly perfused (deadspace), and the dependent lung is poorly ventilated and well perfused (shunting)
See pic on next slide to clearify
Distribution of V/Q: Lateral anesthetized & paralyzed:
picture to explain it visually
Ventilation and Perfusion Lateral Decubitis Summary
Label the chart
V/Q mismatches:
if you have no ventilation and only perfusion what is it
Absolut shunt
V / Q
O / 5 = 0
V/Q mismatches:
what is teh numerical value for shunt?
0
V/Q mismatches:
what is normal V/Q and explain
0.8
V / Q
4 / 5 = 0.8
V/Q mismatches:
if you have ventilation and no perfusion what is it called?
Dead space
V / Q
4 / 0 = infinity
V/Q mismatches:
what is the numerical value for Deadspace?
infinity
V/Q mismatches:
what is a dead unit?
no ventilation and no perfusion
V/Q mismatches:
picture to show
V/Q mismatches:
whata are 3 causes of low PaO2
low inspired O2
Hypoventilation
V/Q mismatch
V/Q mismatches:
the pt is hypoxemic (PaO2
you must calulate and interperate the Alveolar - arterial blood gradient for O2 and/or Co2
PAO2 - PaO2
PAO2 - PaO2 gradient:
what is the normal gradient PAO2 - PaO2 ?
5-15mmHg
PAO2 - PaO2 gradient:
What is normal PaCO2 - PACO2 gradient
2-10 mmHg
PAO2 - PaO2 gradient:
if either ration is increased what does this mean?
there is a V/Q mismatch
PAO2 - PaO2 gradient:
what is normal PAO2 -PaO2 gradient on 100% room air
Problems:
while breathing room air a pt has a PaCO2 of 76mmHg a PAO2 of 55mmHg and a PaO2 of 45mHg. what is the problem V/Q mismatch or hypoventilation?
55-45 = 10
normal ratio so Hypoventilation
Problems:
a pt who is mechanically ventilated has a PaCO2 62 mmHg, and an ETCO2 28mmHg, and a PaO2 of 50mmHg. what is the problem V/Q or hypoventilation
62- 28 = 34 mmHg
abnormal so V/Q mismatch
Problems:
how do you estimate the PaO2 in a healthy pt?
by multiplying the %O2 in the inspired gas by 5
Problems:
how do u estimate the PAO2 in a healthy pt?
multiply the % O2 of the inspired gas mixture by 6
Problems:
est the PaO2 and PAO2, then them do the PAO2 - PaO2 gradient if the pt is breathing an FiO2 of 0.6 (60%)
PaO2 = 60 x 5 = 300
PAO2 = 60 x 6 =360
360 - 300 = 60mmHg
Problems:
a pt who is mechanically ventilated has a PaO2 od 250mmHg, when the inspired O2 is 100%. Does the pt have a V/Q problem?
PAO2 = 6 x 100 = 600
600 - 250 = 350mmHg
yes there is V/Q mismatch
questions:
What si average V/Q
0.8
questions:
what is happening if V/Q = 0
Shunt
right to left
questions:
what is happening if V/Q = infinity
absolute deadspacing
questions:
what is the normal PAO2 -PaO2 different on room air?
on 100% O2
RA= 5-15 mmHg
100% =
questions:
what is indicated if there is an increase in PAO2-PaO2 or PaCO2 - PACO2?
A V/Q mismatch
Shunting or deadspace
questions:
what can cause Shunting
Asthma
CF
tumor
questions:
what can cause Deadspace
PE
clamping
tumor
Summary:
in any position in an AWAKE, SPONT BREATHING, UPRIGHT patient. the ______ region of the lungs are better perfused and ventilated?
dependent
Summary:
why does a shunt cause a right to left shunt?
the blood passes to the left side of the body without being oxygenated.
Summary:
will O2 help the situation if there is a right to left shunt?
no.. the alveoli are empty or blocked can’t get O2 there
Summary:
will O2 help if the problem is hypoventilation or Dead space?
yes
Summary: OLV
Do you CPAP the dependend or NON-dependent lung
Non-dependent
Summary: OLV
do you PEEP the dependent or NON-dependent lung
Dependent
Summary: OLV
if you can do one or the other in OLV, would it be CPAP or PEEP?
CPAP- it has been shown to be a better intervention
